Many commercially available food products, including sterile-treated fruit juice, wine, UHT milk, tomato puree etc., are packed in packages which are manufactured from a previously sterilized or sterile-treated packaging material. A typical example of this kind of package is the parallelepipedal packaging container for liquid or pourable food products, which is known by the name Tetra Brik Aseptic (Registered Trade Mark), which is manufactured by folding and sealing of a web-shaped laminated packaging material. The laminated packaging material comprises layers of fibrous material such as paper, which are coated on either side with a thermoplastic material such as polyethylene. On the side of the laminated packaging material which is destined to be in contact with the food contents of the package, there is also a layer of barrier material, such as e.g., aluminium foil, which is also coated with a thermoplastic layer.
In order to manufacture parallelepipedal packaging containers of this type, filling or packaging machines are fed with laminated packaging material in web form. The packaging material web is sterilized in the packaging machine by the application of a chemical sterilization agent such as e.g., hydrogen peroxide solution. Upon completion of sterilization, the sterilization agent is removed from the surfaces of the packaging material, for example, it may be vaporized by heating. The thus sterilized packaging material web is retained in a closed sterile space and is folded and longitudinally sealed to form a tube. The tube is filled with sterile-treated food product and is transversely sealed and cut into pillow-shaped, filled and sealed packaging containers, which are then mechanically folded to form a parallelepipedal package.
In order to open this type of package, several solutions have been proposed. One solution consisted in the provision of a line of perforations, partially penetrating the outer layers of the laminated packaging material but leaving the internal barrier layer or layers intact, and extending across the corner zone of a flap of the package. By raising the flap and cutting or tearing along the perforations, the package was opened, and the contents could be poured from the package. However, the package could not be reclosed, and thus had to be handled in a careful manner to avoid spillage, until all of the contents were used.
In order to overcome this inconvenience, various types of reclosable opening devices have been proposed. One such solution consisted in the provision of an outlet opening formed in the packaging material laminate and a pull-tab applied over the opening in the filling or packaging machine, with a frame-like pouring device having a reclosable lid connected to the outside of the filled and formed package over the pull-tab. In order to access the contents of the package, a user must first open the lid, and then remove the pull-tab. Once the desired quantity of contents has been removed from the package, the lid can be reclosed.
While this solution is extremely advantageous from many standpoints, it has been found to be susceptible to improvement. Specifically, it would be desirable to have an opening device which permits a user to open the above-described type of package in a single operation, and thereafter provide the possibility of package reclosure with improved liquid-tightness.
Laid-open Japanese Patent No. 63-149818 describes an opening device used for packages of the gable-top type, which are usually formed from a packaging material blank on a mandrel and are particularly suitable for pasteurised food products. The opening device has a frame affixed to one of the two inclined walls of the gable-top package and bearing two upright sem-icircular walls. A lever having a matching semi-circular configuration is journalled between the walls for rotation about an axis passing substantially through the centres of the planar bases of the semi-circular walls, parallel and adjacent to the surface of the package. The lower portion of the lever facing the package has teeth for rupturing the packaging material, and a grip-tab, whereby a user can open the package by rotating the lever in one direction, and reclose the package by rotating the lever in the opposite direction.
However, this kind of opening device requires the application of significant force in order to drive the teeth through the packaging material. This may lead to inadvertent spillage of the contents of the package. Furthermore, the excessive force exerted on the points whereat the lever is journalled to the walls, may cause damage to or even breakage of the device. Moreover, although the device can be reclosed after opening, the reclosure is not liquid-tight, whereby spillage may occur in the event that a reclosed container is accidentally knocked over.
A screw cap provides a better degree of liquid-tightness when reclosed, but when using a screw cap on an aseptic package of the above-described type, some provision has to be made for rupturing the barrier layer of the container at the time of opening, so as to maintain the aseptic quality of the package, right up to the moment when the package is opened for consumption of the product contained therein.
Known from laid-open Japanese Patent Application No. 63-156928 is a three-piece opening device consisting of a frame having an externally threaded portion, a screw-cap which can be screwed onto the frame, and a sleeve located in a tubular portion of the frame and having a lower toothed edge which, when actuated by screwing the cap onto the frame, perforates the laminated packaging material of a container. However, this device has the sleeve part in addition to the cap and frame, and is therefore more expensive to manufacture and assemble with respect to traditional screw caps. Furthermore, the cutting action of the toothed edge can cause severed fragments of packaging material to fall by gravity into the underlying food product contained in the package.
Laid-open Japanese Patent Application No. 64-2727 describes an opening device, for the above-mentioned gable-top type of package. This latter device has a frame defining a tubular portion, a sleeve arranged slideably within the tubular portion and connected to the frame by a collapsible bellows, and a cap hinged to the frame and overlying the open uppermost end of the sleeve in a closed position. A user has to apply pressure on the cap, which is transferred to the sleeve, thereby collapsing the bellows. The lower end of the sleeve punctures the packaging material of the container and the reclosable cap can be opened to pour the contents.
However, the cap can be knocked during handling and transportation, thereby inadvertently collapsing the bellows and causing the sleeve to puncture the underlying packaging material. Furthermore, the perforating action of the sleeve can cause severed fragments of packaging material to fall by gravity into the underlying food product contained in the package.